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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec8ea1c6cb2811f8dfcb5d79e66cbd7946897fd901d368ed8546c12a4a6ce8e3' 
  AND token = '4u+LusJBSA67JinPOxkdJg3zA/yPv/lt1yvUYnnq2sQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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