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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51ff7ed3a8fce85149c4d38095677f1e0a399ad9ff12d1ebe4d3cb3ce743255b' 
  AND token = 's0+l/ydqasbhc4WijC1Qst0sxvBHJdYeRBDV5Xq9GRM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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