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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3ad36ad5c8c836619323628b5c720d17e795fdba3ee1703b1498234db395d5c' 
  AND token = 'jNToVXfDtl1j7Mce+xkR+0hmagF0P3FCg6BVd6Ls3+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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