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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a31938714b62353701de1eeaddc13d26b666b68654cfbd66fb4a0cde8b6e65ff' 
  AND token = 'o5Dwi1xaXDLZ2Tmo3I66Nw6y9p99ldtLNDuwc8lk3Kw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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