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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c638718237739bb12b20872e21f496166e949bb61df9f07aec088cc68de84b3' 
  AND token = 'V2ljcBMUuG9XRHCmUVMdegPXffFzRG7KzLdXMHWpbIs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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