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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c51a43b00e6c05cb90918b0f023c0e5d52d2aecff1a2c37f30b8d9f2266c4c8' 
  AND token = 'lx1XDebIei5Go5t5czIR1lBaD3sd4tUtW4YspDT4KF0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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