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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c51b17da160b4fc1ff8cf88f4768a4c36779d1c14df085c13db8ca6685a492a8' 
  AND token = '8OU4WV2+Gl5NEDDo/ruYVle756EXeVpRLIVaM51BhCo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}