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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df31ac73437928965f063e0f8f50ba3d7ca76d5a9e74d42707d62b80c7d98fb2' 
  AND token = 'i6ZHeyJ5EfixbXsEe8xQ15gfB7QB/EDYCEe4Y6Tv15Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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