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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'de8d71975d90bbe03cea78966ecbc35d4c3bba1be4a70f6ce560d80f5acdbbb3' 
  AND token = '6EH47SXPCoUT7kAf+G2k4sn4j2X1IuiAldmcGTtE3Ao=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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