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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b0c519f9b5eb06800f6fa1fb07ce579e8ef716a628e2a5315ff89380c24067' 
  AND token = 's1UgYy4lZ6bpdZIRN0H7LBvmJ/sWZA9QUnu2Pxg7X9s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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